My 1979 Hunter 33 is equipped with a 15hp Yanmar. The engine runs very well but after running for about an hour the overheating alarm sounds. A machanic said the water jackets in the engine block are partially blocked due to the engine having soo many years of service in saltwater. The machanic attempted to cleanout the block by putting vingar then acid in the block. The engine is heating to over 160 degrees causing alarm overheating alarm to sound but the machanic tells me a check with a lazer thermometer shows the engine is not getting "that much" over thje 160 degrees to pose an immediate problem. Does anyone known of a way I can get the engine to cool down and get another year of use before replacing the raw water cooled Yanmar with a new freshwater cooled engine. The waterpump impeller has been replaced.
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R
red coles
Waterflow
Hello Mike: The main thing to look for is good waterflow. Check exhaust and see if you get good spurts of water. I recently had to change my mixing elbow ( not a big job) due to low flow. Remember all the cooling water tha goes thru the engine has to exit the exhaust. So if no flow, water stays in block and overheats. You may also want to test your thermostat. A simple test is to remove the cooling hose at the elbow, start engine and see if you get good flow. If not work back. If yes, work forward. Only run engine long enough to make test (<30 sec.) Good luck red
Hello Mike: The main thing to look for is good waterflow. Check exhaust and see if you get good spurts of water. I recently had to change my mixing elbow ( not a big job) due to low flow. Remember all the cooling water tha goes thru the engine has to exit the exhaust. So if no flow, water stays in block and overheats. You may also want to test your thermostat. A simple test is to remove the cooling hose at the elbow, start engine and see if you get good flow. If not work back. If yes, work forward. Only run engine long enough to make test (<30 sec.) Good luck red
P
Pete
COOL YANMAR
your mechanic sounds like he knew what he was doing and is correct that even above 160 degrees it will be ok just don't run hot to the point of boiling the water and steam exhaust. Water flow is the key to cooling, you might want to try another vinegar and acid bath ,you may want to try removing the thermostat to see if that helps improve water flow and run cooler. The exhaust elbow is always suspect and will assume that your mechanic checked it. If all you really need is another year on the engine even running "hot" it should last that long or longer (assuming less then 200) Good Luck!
your mechanic sounds like he knew what he was doing and is correct that even above 160 degrees it will be ok just don't run hot to the point of boiling the water and steam exhaust. Water flow is the key to cooling, you might want to try another vinegar and acid bath ,you may want to try removing the thermostat to see if that helps improve water flow and run cooler. The exhaust elbow is always suspect and will assume that your mechanic checked it. If all you really need is another year on the engine even running "hot" it should last that long or longer (assuming less then 200) Good Luck!
Try this out - Marsolve
Mike: Here is a product that is suppose to clean 'em out. It is called Marsolve. It is a biodegradeable product so you should be able to pump it thru your engine just like non-toxic antifreeze. The stuff is suppose to be mixed 50/50 so one gallon of the stuff should do the trick. I would think that about 2-4 hours of letting it sit in you system should do the job. Let me know what you think. At $25/gal and another $5-6 for shipping, it's cheaper than dealing with a maniac (make that mechanic). http://www.marsolve.com/
Mike: Here is a product that is suppose to clean 'em out. It is called Marsolve. It is a biodegradeable product so you should be able to pump it thru your engine just like non-toxic antifreeze. The stuff is suppose to be mixed 50/50 so one gallon of the stuff should do the trick. I would think that about 2-4 hours of letting it sit in you system should do the job. Let me know what you think. At $25/gal and another $5-6 for shipping, it's cheaper than dealing with a maniac (make that mechanic). http://www.marsolve.com/
P
Paul Akers
You didn't mention...
...at what RPM you run your engine. If you are talking about full throttle, then kick it back to a maximum of 80% throttle. Yanmars don't like full throttle. But if you are running at normal speeds, then check the thermostat.
...at what RPM you run your engine. If you are talking about full throttle, then kick it back to a maximum of 80% throttle. Yanmars don't like full throttle. But if you are running at normal speeds, then check the thermostat.
J
Joe Gooch
Final Solution
Mlike, If after you have tried these other suggestions you still have the problem and if you really want the final solution, take the head off the engine, have it boiled out at a radiator ship and physically remove what is in the block and put it back together. My 1980 engine was so clogged that water could not flow from the head to the block because the water holes were actually plugged shut; I had to physically knock a hole through the rust etc. where a hole should be. This is the FINAL SOLUTION. Good Luck, Joe
Mlike, If after you have tried these other suggestions you still have the problem and if you really want the final solution, take the head off the engine, have it boiled out at a radiator ship and physically remove what is in the block and put it back together. My 1980 engine was so clogged that water could not flow from the head to the block because the water holes were actually plugged shut; I had to physically knock a hole through the rust etc. where a hole should be. This is the FINAL SOLUTION. Good Luck, Joe
T
Tim Schaaf
Pete is right...
Sometimes you do have to remove the scale that way. But, the water passages are actually pretty big, since the engine is designed for salt water use. If you take off the plate into which the aft zinc is mounted, you can get a really good look at the passages in the head. I have even been known to poke around in there with a screwdriver and knock some of the scale loose....there is a lot of room. But chemical removal is much better. The previous posts give good advice, although I disagree with two points: first of all, your engine should be working MUCH cooler than it is....heating a raw water engine to 160 degrees is exactly what causes the scale to be deposited. This is generally thought of as the red line temperature, and it is way less than boiling. Secondly, a correctly maintained and propped Yanmar will run indefinitely at full throttle without overheating. There are other issues which dictate that you should not run it flat out for more than about an hour, but if correctly propped, etc., overheating is not one of them. If you are overpropped, however, or the boat is very overloaded (which will result in greater wetted surface area, hence greater drag which will keep the engine from reaching full revs, ie. causing it to be overpropped, even with the standard one) you can overheat the engine. The old saltwater Yanmars are extremely reliable, more bulletproof than the later ones, but the H33 is the very limit of what that 15 horsepower beast can drive. It is very easy to be overloaded. My guess is that you will find a problem with your exhaust elbow or elsewhere in your exhaust system. Good luck. That engine has got YEARS of life, yet.
Sometimes you do have to remove the scale that way. But, the water passages are actually pretty big, since the engine is designed for salt water use. If you take off the plate into which the aft zinc is mounted, you can get a really good look at the passages in the head. I have even been known to poke around in there with a screwdriver and knock some of the scale loose....there is a lot of room. But chemical removal is much better. The previous posts give good advice, although I disagree with two points: first of all, your engine should be working MUCH cooler than it is....heating a raw water engine to 160 degrees is exactly what causes the scale to be deposited. This is generally thought of as the red line temperature, and it is way less than boiling. Secondly, a correctly maintained and propped Yanmar will run indefinitely at full throttle without overheating. There are other issues which dictate that you should not run it flat out for more than about an hour, but if correctly propped, etc., overheating is not one of them. If you are overpropped, however, or the boat is very overloaded (which will result in greater wetted surface area, hence greater drag which will keep the engine from reaching full revs, ie. causing it to be overpropped, even with the standard one) you can overheat the engine. The old saltwater Yanmars are extremely reliable, more bulletproof than the later ones, but the H33 is the very limit of what that 15 horsepower beast can drive. It is very easy to be overloaded. My guess is that you will find a problem with your exhaust elbow or elsewhere in your exhaust system. Good luck. That engine has got YEARS of life, yet.
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